Coughing is a benign reflex, a protective response of the body to respiratory secretions or harmful factors, but chronic or severe coughing over a long period of time can affect daily work and life. What are the criteria for distinguishing acute and chronic coughs? Coughs are usually divided into 3 categories according to their duration: acute cough, subacute cough and chronic cough. 1. Acute cough <3 weeks 2. Subacute cough 3-8 weeks 3. Chronic cough ≥8 weeks Acute and subacute coughs are usually seen in acute bronchitis, acute sinusitis, allergic rhinitis, acute attacks of chronic bronchitis, and bronchial asthma (asthma for short), which are relatively simple to treat clinically because they usually have an acute onset and a clearer cause. Chronic coughs lasting ≥8 weeks should be treated more vigilantly, as their causes are often more insidious and not easily detected. When chronic cough occurs, how should it be diagnosed and treated? I believe the following process should be followed: 1. Initial X-ray chest radiographs should be performed, and if infectious diseases such as pneumonia, tuberculosis, or occupational diseases such as lung cancer are found, they should be treated according to the cause. If no abnormality is found in the X-ray chest film, see Article 2. 2. At this time, the following 4 causes of chronic cough should be considered: (1) Postnasal drip syndrome It can also be understood as a syndrome in which various nasal, pharyngeal, and laryngeal pathologies cause secretions to back up behind the nose and throat, or even back up into the voice box or trachea, resulting in a cough as the main manifestation. Clinical manifestations: In addition to cough and sputum, patients usually complain of flu drip in the throat, mucus adhesion in the oropharynx, frequent throat clearing, throat itching or nasal itching, nasal congestion, runny nose, sneezing, and so on. Sometimes patients complain of hoarseness, and speech may trigger coughing, but other causes of coughing itself may also have such complaints. The onset is usually preceded by a history of upper respiratory tract disease (e.g., cold). (2) Cough variant asthma is a special type of asthma in which cough is the only or main clinical manifestation without obvious symptoms or signs such as wheezing or shortness of breath, but with airway hyperresponsiveness (confirmed by bronchial excitation test). The main manifestation is a diarrheal dry cough, usually violent, with nocturnal coughing as an important feature. Cold, cold air, dust and fumes can easily trigger or aggravate the cough. (3) Gastroesophageal reflux cough As the name suggests, the cough is caused by the reflux of gastric juice or gastric contents into the esophagus due to malfunction of the stomach and esophagus, and is characterized by a cough with a burning sensation behind the sternum, acid reflux, belching and chest tightness. In some patients with a small amount of gastric reflux into the throat and subsequent aspiration into the trachea, cough symptoms and throat symptoms are more likely to occur early. The cough mostly occurs in the daytime and in the upright position, with a dry cough or a small amount of white mucous sputum. (4) Eosinophilic bronchitis causes cough, a non-asthmatic bronchitis characterized by airway eosinophil infiltration. The main symptom is a chronic irritant cough, which is often the only clinical symptom, usually a dry cough with occasional little mucous sputum. Some patients are sensitive to fumes, dust, odors or cold air, which are often triggering factors for coughing. Patients do not have symptoms such as shortness of breath or dyspnea. Pulmonary ventilation function and peak expiratory flow rate variability are normal, and there is no evidence of airway hyperresponsiveness. From the above four etiologies we can see that chronic cough with different causes has different characteristics and its treatment principles are often far apart, making it easy to misdiagnose and mis-treat the disease in an acute manner. The cough as a benign reflex of the organism in response to a lesion, on the contrary, blindly suppressing the cough can conceal the cause and delay the condition. Therefore, when chronic cough occurs, it is still recommended to go to a regular hospital for standardized examination and to receive standardized treatment.